In metalworking operations where a workpiece is machined, equipment of some type is necessary to hold the workpiece in position in a machine tool so the machining process can be successfully carried out. This type of equipment is known as “workholding” equipment. In the production of toothed articles, such as gears, workholding equipment can be generally categorized as two types, chucks and arbors.
Chucks hold a workpiece by contracting a component called a “collet” around the workpiece or a component thereof. For example, when a bevel or hypoid pinion with integral shaft is placed in a chuck, it is usually the shaft that is gripped by the collet which has been reduced in diameter (i.e. contracted) to grip the shaft to hold the pinion in position for machining. Examples of chucks for gripping pinion shanks can be found in U.S. Pat. No. 3,083,976 to Stark and U.S. Pat. No. 3,244,427 to Taschl.
Arbors grip a workpiece by expanding a collet into contact with a surface of the workpiece. As an example, a bevel ring gear is placed on an arbor and the collet is expanded until contact of sufficient force is established with the surface of the bore of the ring gear to hold the ring gear in position during machining. An example of an arbor for a ring gear can be found in U.S. Pat. No. 3,735,994 to Jaehn. An arbor for expanding into contact with the bore of a pinion can be found in U.S. Pat. No. 3,517,939 to Jaehn.
In either chucks or arbors, the force necessary to contract or expand the collet mechanism is provided by a draw bar (or draw rod) in the machine tool. The draw bar is advanced and/or retracted usually via a hydraulically operated piston. Movement of the draw bar in the axial direction of the chuck or arbor usually causes opposed angled surfaces of components within the workholding equipment to slide relative to one another resulting in inward (contracting) or outward (expanding) movement of the collet to grip a workpiece or component part thereof. Generally, one angled surface is found on the collet and the other angled surface is found on an actuator attached to the draw bar or on the draw bar itself.
Chucks and arbors are mounted for rotation in the bore of a spindle of a machine tool. The spindle bore is usually tapered and a similar taper is usually found on the outer surface of the chuck or arbor. Once placed in the spindle bore, a plurality of bolts are extended through holes in a mounting flange, located about the spindle, and into engagement with corresponding threaded holes in the face of the machine spindle.
Securing a chuck or arbor to a machine tool spindle, or ejecting it from the machine tool spindle, are manually performed operations that are very time consuming since the many bolts must be tightened to specifications. When removing the chuck or arbor, aside from the time necessary to loosen and remove all of the bolts, ejector screws usually must be utilized to “break” (i.e. un-seat) the contact between the chuck/arbor outer tapered surface and the tapered inner surface of the spindle bore.
U.S. Pat. No. 6,260,855 to Curtis teaches a workholding apparatus in which action of a draw bar effects gripping and release of a workpiece but also effects the seating of a chuck or arbor being positioned in a machine spindle as well as the un-seating of a chuck or arbor from its seated position in a machine spindle. The apparatus includes sets of spaced apart lugs that must pass by similarly spaced lugs on a draw bar and sleeve when inserting the apparatus in a spindle. Once inserted, the apparatus is turned to align the lugs thereby establishing contact between the apparatus and the draw bar. A stop mechanism is also included on the draw bar to prevent inadvertent forward movement of the draw bar when de-chucking a workpiece.
It is an object of the present invention to provide a means to simplify the installation of a chuck or arbor in a machine spindle and its removal from the spindle while eliminating some components of the chuck or arbor thereby saving time and reducing material and assembly costs.